The present invention is directed to bicycles and, more particularly, to a motorized bicycle derailleur.
Many current bicycles have electronically controlled bicycle components. For example, some bicycles include automatic transmissions wherein electronically motorized front and rear derailleurs are automatically controlled by a microcomputer based on bicycle speed. One type of motorized derailleur includes a motor that is spaced apart from the derailleur and connected to the derailleur by a conventional Bowden cable, wherein the motor pulls and releases the inner wire of the Bowden cable to operate the derailleur. Another type of motorized derailleur integrates the motor with the derailleur so that the motor drive shaft directly moves the derailleur linkage mechanism. Such a configuration eliminates the requirement of a Bowden cable, thus making the overall derailleur mechanism more compact.
While a derailleur with an integrated motor has many advantages, it also has drawbacks. For example, the derailleur itself must be made larger to accommodate the motor and related components. Since the derailleur is mounted to the side of the bicycle frame, the larger derailleur protrudes laterally more than a conventional derailleur. This, in turn, creates the risk that the derailleur may be struck by rocks or other obstacles when riding in rough terrain, or that the derailleur is damaged or destroyed if the bicycle falls over.
Some motorized derailleurs include gear reduction mechanisms comprising a plurality of variably sized interconnected gears so that higher speed, low torque motors may be used to precisely move the derailleur linkage mechanism. If the motor is integrated with the derailleur, then the gear reduction mechanism also must be integrated with the derailleur. Typically, the gear reduction mechanism is incorporated within the derailleur base member that mounts the derailleur to the bicycle frame. In such cases, the pivot shafts for the variably sized gears are attached to the base member, and possibly to the derailleur linkage mechanism and/or to the motor drive shaft. As a result, the entire derailleur sometimes must be disassembled in order to service the motor or the gear reduction mechanism. Furthermore, sometimes the pivot shafts are permanently mounted to the base member, to the linkage mechanism and/or to the motor drive shaft such that the entire derailleur must be replaced if the gear reduction mechanism is worn or damaged.